<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    .box{
        width: 300px;
        height: 300px;
        border:1px solid black;
    }
</style>
<body>
    <button>发送请求</button>
    <div class="box"></div>
</body>
<script>
    addEventListener('load',function(){
        const btn = document.querySelector('button');
        const box = document.querySelector('.box');
        btn.addEventListener('click',function(){
        const xhr = new XMLHttpRequest();
        xhr.open('POSt','http://127.0.0.1:8000/post');
        //设置请求头
        xhr.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
        //自定义请求头
        xhr.setRequestHeader('name','atguigu');//setRequestHeader设置请求头('名称'，值);
        xhr.send('a=1&b=2&c=3&d:4');//post中发送参数请求体
        xhr.onreadystatechange = function(){
            if(xhr.readyState == 4){
              if(xhr.status >=200&&xhr,status <300){
                console.log(xhr.status);//状态码
                console.log(xhr.statusText);//状态字符串
                console.log(xhr.getAllResponseHeaders());//所有响应头
                console.log(xhr.response);//响应体
                 box.innerHTML = xhr.response;
              }
            }
        }            
        })
    })
</script>
</html>